Nowadays, integrated circuits (ICs) may comprise a plethora of sensors, such as gas sensors, relative humidity (RH) sensors, specific analyte detection sensors, and so on. Such sensors may be included in the IC design for a number of reasons.
For instance, a gas sensor may be included in an IC to detect a change in the ambient conditions of a product tagged with the chip such that product quality control can be achieved by monitoring the sensor readings of the chip. This can for instance be used to accurately predict the remaining shelf life of the product, e.g. perishable food stuff. The gas sensor may for instance be adapted to determine changes in the CO2 content of the ambient atmosphere. Alternatively, the gas sensor may be used to detect changes in the gas composition of larger environment such as buildings or may be used in medical application domains, e.g. in breathing apparatuses.
With the ongoing diversification of electronic devices or electronic information gathering such as by RF tags on packaged articles, it is often desirable to include different types of sensors in a single IC. For instance, the detection of other environmental parameters, for instance temperature and humidity such as for HVAC (heating, ventilation and air conditioning) control in buildings and cars, are particularly desirable in certain application domains. In addition, sensing of analytes of interest, e.g. CO2, may be desirable in such application domains. However, it is difficult to manufacture CO2 sensors having the desired sensitivity in a cost-effective manner. In particular, impedometric CO2 sensors, i.e. sensors based on measuring the change in the impedance of a material based on its exposure to CO2, suffer from relatively poor sensitivity.
Multiple sensor ICs are known per se. However, most solutions are based on a system comprising multiple discrete sensors, which makes the system bulky and rather expensive. Also, the manufacturing process can be rather complex, especially when sensors with high sensitivity are to be included in the design. This negatively impacts on production yield and pushes up the price of the known good products.